It was a long time coming - 24 years after they were convicted on murder charges and three years since new DNA evidence raised questions about their guilt.

On Friday, New Jersey's attorney general said a lengthy independent investigation into how the case went sideways was finished. Mistakes were made, authorities acknowledged.

What mistakes? They weren't saying.

Still, the case could lead to significant reforms in how prosecutors in the Garden State handle wrongful conviction claims, according to a letter sent by Attorney General Gurbir Grewal to New Jersey's 21 county prosecutors, a copy of which was obtained from his office by NJ Advance Media.

It comes as Grewal is weighing the creation of a statewide conviction review unit to deal with cases that may have put innocent people behind bars.

The letter included recommendations from former state Supreme Court Chief Justice James Zazzali, who led the post-mortem examination and outlined six steps for prosecutors to avoid more embarrassing episodes of botched convictions.

The memo encouraged law enforcement officials to be more open to DNA testing and to "treat the long saga endured by Eric Kelley and Ralph Lee as instructive and cautionary."

Grewal's letter noted that Kelley and Lee hadn't been declared innocent before prosecutors abruptly dropped their charges, and Zazzali's review "uncovered no evidence of foul play or illegal conduct" by prosecutors or police.

The investigation did find "'some matters' that could have or should have been handled differently," the letter said, but exactly what those problems were remains unclear.

Grewal did not return a message seeking comment Friday, and a spokeswoman declined to answer questions about missteps revealed by the inquiry. Passaic County Prosecutor Camelia Valdes, whose office spent years fighting the release of Kelley and Lee, did not respond to a message seeking comment.

Asked for a copy of the full "confidential" report by Zazzali and Kevin Walsh, a colleague at the politically connected law firm, Gibbons P.C., the Attorney General's Office declined to release it, telling a reporter to file a public records request for the document.

The long saga of Kelley and Lee started with the slaying of a Paterson video store clerk. Tito Merino, 22, was working in his uncle's store, Victoria Video when he was viciously stabbed and beaten in a 1993 robbery.

Based on a confidential tip, Paterson police zeroed in on Kelley, Lee and another man as suspects, and quickly obtained signed confessions from Kelley and Lee. The pair later recanted, saying they confessed only under pressure from police, and prosecutors later dropped the charges against the third man. But Kelley and Lee were convicted at separate trials.

Decades later, two legal groups dedicated to freeing the wrongly convicted - the Innocence Project and Centurion Ministries - obtained new DNA testing and other testimony that contradicted the pair's signed confessions.

A hat that police said was left behind by the killer was later swabbed and re-tested, the results ruling out Kelley and Lee as its owner. When the DNA profile was run through a federal database of convicted felons, it matched a former Paterson man who served time for a similar crime.

Prosecutors in Passaic County insisted they had the right men, even arguing in court documents that the other man was innocent of the crime. Coverage of the case by NJ Advance Media prompted further scrutiny.

After a Superior Court judge overturned the convictions of Kelley and Lee, and prosecutors lost an appeal, the Attorney General's Office took over the case and announced Zazzali's review.

But Grewal disclosed in his Friday letter that the investigation "did not find sufficient evidence to pursue criminal charges against any other individuals for Merino's murder," meaning the store clerk's killer may never face justice.

It's still unclear what missteps were uncovered by the attorney general's review of the case, but Zazzali's memo included six recommendations for preventing future black eyes for the justice system.

They included always investigating when DNA points to a potential other suspect, meeting with defense attorneys who raise "strongly exculpatory evidence," notifying top prosecutors about new evidence and not opposing efforts by defendants to get new DNA testing in many cases.

Paul Casteleiro, an attorney for Centurion Ministries who represented Lee, said those steps weren't taken by prosecutors who handled the Paterson case.

When new DNA evidence surfaced, he said, "they not only didn't investigate, they absolutely refused to investigate."

The attorney general's review found prosecutors should do more to make sure they haven't imprisoned innocent people in their quest for justice.

"The duty of law enforcement is not solely to obtain and protect convictions, but rather to ensure that justice is done in every case, for victims and defendants alike," Zazzali and Walsh wrote.

In his letter, Grewal said he was forming a working group to create new guidelines on handling DNA cases in New Jersey.

That development comes as a separate panel, led by former state Supreme Court Justice Virginia Long and former New Jersey U.S. Attorney Paul Fishman, is expected to release recommendations to the attorney general about establishing a formal conviction review unit in his office.

S.P. Sullivan may be reached at ssullivan@njadvancemedia.com. Follow him on Twitter. Find NJ.com on Facebook.